if you wanted to save some money keep your stock silencer it performs very well and you probably wouldn't notice a difference with an fmf unit, only real advantage is weight, i would take that money you were going to use on the silencer and have your carb bored by RB card designs, i have a 99 kdx220 with the carb bore and fmf rev pipe but stock silencer, i do have the fmf turbine core II silencer as well but don't use it, i'll sell ya mine if you really want one, and these two mods will really wake your bike up, also do the airbox mod, and some boysen power reeds or the DFII, check out
www.rockymountainmc.com they have very good prices and also check out Fredette racing products too,
www.frpoffroad.com